1. Field of Invention
The invention relates to instruments for measuring or sensing fluid pressure and, more particularly, to structures which accomplish such sensing by the expansion of a member under the fluid pressure being sensed. Reference is made to Rockstead et al. U.S. Pat. No. 3,844,173.
2. Description of Prior Art and Summary of Invention
Heretofore, it has been proposed to mount an electro-mechanical sensing device, such as a strain gage or the like, on the surface of a diaphragm mounted across a pressure vessel in order to sense the deflection of the diaphragm as a function of fluid pressure in the vessel. In such instance, the amount of movement sensed by the strain gage is necessarily small and, as a result, the signal-to-noise ratio is poor. Also, the relationship between displacement at the strain gage and the fluid pressure being monitored is non-linear, thus requiring the use of relatively complicated electric circuits and components to obtain reasonable accuracy and correction for the non-linearity. One of the principal features of the present invention is that the structure provides a motion multiplication configuration whereby the displacement at the strain gage per unit of length of the strain gage is much greater than the displacement at any point on the surface of the member being stressed, thus dramatically increasing the signal-to-noise ratio; and of equal importance, the structure provides a substantially perfect linearity between the signal and the pressure being monitored.
Another object of the present invention is to provide a fluid pressure-sensing device of the character described which provides excellent sensitivity with minimum required displacement, thus enabling the device to function in the lower region of the stress/yield curve where the lineal relation of Hooke's Law applies, and to accomplish the foregoing without the use of complex, expensive signal-amplifying and correcting circuits.
A further object of the present invention is to provide a fluid pressure-sensing device of the character above which is of simple, straightforward construction using common, relatively available materials in a compact configuration which will provide safe, dependable, accurate and repeatable operation over an indefinitely long period of use.
Still another object of the present invention is to provide a fluid pressure-sensing device of the character described which is well adapted for miniaturization in which all of the parts may be constructed in compact form and rugged materials affording large overload capacity without permanent deformation.
The invention possesses other objects and features of advantage, some of which of the foregoing will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of this specification. It is to be understood, however, that variations in the showing made by the said drawing and description may be adopted within the scope of the invention as set forth in the claims.